1. What is the precision casting of stainless steel?
In the production of stainless steel products, some products have strange shapes and cannot be produced by bending and other processes. To produce such products with irregular shapes (hollow or solid inside), a wax mold is used to make a sand mold. →The process of filling and molding with liquid material.
Advantages: Products with various styles can be made according to different wax models.
Disadvantages: The precision of the forming blank is not high, and the surface roughness is large.
2. The precision casting process
1. Make molds according to different shapes of products. The mold is divided into upper and lower concave molds and is completed through comprehensive processes such as turning, planing, milling, etching, and EDM. The shape and size of the pit are the same as the half of the product. Because wax molds are mainly used for industrial wax pressing, aluminum alloy materials with a low melting point, low hardness, low requirements, low price, and lightweight are used as molds.
2.Use aluminum alloy molds to produce a large number of industrial wax solid-core models. Under normal circumstances, an industrial wax solid-core model can only correspond to one rough product.
3.Refine the margin around the wax mold. After deburring, stick a plurality of single wax molds on the pre-prepared mold head (also known as the group tree). This mold head is also an industrial wax solid produced by wax mold. core model. (looks like a tree)
4.Coat the wax molds fixed on the die head with industrial glue and spray the first layer of fine sand (a kind of refractory sand, high-temperature resistance, usually silica sand) evenly. The grains of this sand are small and fine, which ensures that the surface of the final blank is as smooth as possible.
5.Let the wax mold sprayed with the first layer of fine sand air dry naturally at the set room temperature (or constant temperature), but it cannot affect the shape change of the internal wax mold. The natural air-drying time depends on the complexity of the product itself. The first air-drying time of the casting is about 5-8 hours.
6.After the first sandblasting and air drying, continue to apply industrial glue (silica soluble slurry) on the surface of the wax mold and spray the second layer of sand. The particle size of the second layer of sand is larger than that of the first layer of sand. Come big, come thick. After spraying the second layer of sand, let the wax mold air dry naturally at the set constant temperature.
7.After the second sandblasting and natural air drying, the third sandblasting, the fourth sandblasting, and the fifth sandblasting are carried out by analogy. Requirements: – Adjust the blasting times accordingly according to the product surface requirements, volume size, self-weight, etc. Under normal circumstances, the number of sandblasting is 3-7 times. – The size of the sand in each blasting is different. Usually, the sand in the subsequent process is coarser than that in the previous process, and the drying time is also different. Generally, the production cycle of sanding a complete wax mold is about 3 to 4 days.
8.Before the baking process, the wax mold that has completed the sandblasting process is evenly coated with a layer of white industrial latex (silicon soluble slurry) to bond and solidify the sand mold and seal the wax mold. Prepare for the baking process. At the same time, after the baking process, the brittleness of the sand mold can be improved, which is convenient for breaking the sand layer and taking out the blank.
9.Baking process Put the wax mold fixed on the die head and complete the sandblasting and air-drying process into a metal-sealed special oven for heating (usually a steam furnace for burning kerosene). Because the melting point of industrial wax is not high, the temperature is about 150゜, and the wax mold is heated and melted to form wax water flowing out along the gate, this process is dewaxing. The wax model that has been dewaxed is just an empty sand shell. The key to precision casting is to use this empty sand shell. (Generally, this wax can be used repeatedly, but these waxes must be re-filtered, otherwise, the unclean wax will affect the surface quality of the blank, such as surface sand holes, pitting, and also affect the shrinkage of the precision casting product).
10.Baking the sand shell To make the dewaxed sand shell more firm and stable, the sand shell must be baked before pouring the stainless steel water, usually in a high temperature (about 1000゜) furnace.
11.Pour the stainless steel water that has been dissolved into a liquid state at high temperature into the dewaxed sand shell, and the liquid stainless steel water will fill the space formed by the wax mold until it is filled, including the middle part of the die.
12.The factory must detect the percentage of materials because different components of materials will be mixed in the boiler of molten stainless steel. Then adjust the release according to the desired ratio, such as adding those aspects, to achieve the desired effect.
13.After the liquid stainless steel water is cooled and solidified, the outermost sand shell is smashed with the help of mechanical tools or manpower, and the exposed solid stainless steel product is the shape of the original wax mold, that is, the final required raw casting. Then it will be cut one by one, separated and rough ground to become a single raw casting.
14.Inspection of raw castings: raw casting with blisters and pores on the surface must be repaired with argon arc welding, and in serious cases, the waste products should be cleaned and returned to the furnace.
15.Cleaning the raw castings: The raw castings that have passed the inspection must go through the cleaning process.
16.Carry out other processes until the finished product.
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